When a weak female screw makes it impossible to obtain a high tightening force while directly tapping into a work comprising a light metal such as aluminum, plastics, or cast iron, it is conventional practice to use a spiral coil insert for the purpose of guaranteeing a high reliable screw tightening.
There are a tanged spiral coil insert and a tangless spiral coil insert, but the tanged spiral coil insert requires an operation of removing a tang, after being attached to a work, and further an operation of collecting the tang removed. Therefore, the tangless spiral insert, which does not require such operations, is occasionally used.
A patent literature 1 discloses an attachment tool for such a tangless spiral coil insert.
This will be described below with reference to FIGS. 7 to 9 appended to the present patent application.
An attachment tool 300 is provided with a tubular member 301, and a mandrel assembly 302 supported by the tubular member 301. A pivotal claw 303 is disposed in a hollow 304 formed in a longitudinal direction of the mandrel assembly 302, and the pivotal claw 303 is provided with a hook section 305 engaging with a notch 101 (FIG. 9) of an end coil section 100a of a tangless spiral coil insert 100 at one leading end thereof.
In this example, the pivotal claw 303 is biased about a pivotal shaft 307 by a spring 306, and, the pivotal claw 303 is configured to pivot on the pivotal shaft 307 so that the hook section 305 sinks into the notch 101 of the end coil section 100a on a coil-insertion direction outlet side of the coil insert 100 when the mandrel assembly 302 moves in a direction of an arrow 308 and the other end 309 of the pivotal claw 303 has entered a hole formed in the mandrel assembly 302.
The attachment tool 300 for a tangless spiral coil insert described in the patent literature 1 was excellent in operability, but in particular the mandrel assembly 302 provided with the pivotal claw 303 was complex in structure, and was difficult to manufacture or assemble, and accordingly resulted in a factor in high product cost.
Therefore, the present inventor proposed an insertion tool described in a patent literature 2.
That is, as shown in FIGS. 6(a) and 6(b) appended to the present patent application, the insertion tool described in the patent literature 2 is provided, for inserting a tangless spiral coil insert 100 (see FIGS. 7 and 9) to a work, with a mandrel 41 a leading end section of which is constituted as a screw shaft 45, and a pivotal claw 80 which is a slender member and is provided with an actuation section 82 provided at one end thereof with a claw section 81 engaging with a notch 101 of an outlet-side end coil section 100a of the tangless spiral coil insert 100 screwed to the screw shaft 45 and a support section 83 formed integrally with the activation section 82. The pivotal claw 80 is attached to a pivotal-claw attachment groove 71, the support section 83 is pivotally attached to the mandrel 41 by a pivotal shaft 84, and biasing means 88 (88a, 88b) acts on the support section 83 to bias the claw section 81 outward in a radial direction of the screw shaft 45 such that a hook section 90 formed in the claw section 81 elastically engages with the notch 101 of the tangless spiral coil insert 100.
An insertion tool for a tangless spiral coil insert having thus configured is simple in structure and easy in manufacture and assemble as compared with a conventional tool, and, accordingly it can be reduced in manufacturing cost, and besides, is excellent in operability.